Seat Alhambra Diesel Engine Performance Issue

Reduced engine power and poor response on a diesel often points to sensor issues. Does your Alhambra have the ASZ engine? I had a similar problem on my Seat Leon. Have you checked for vacuum leaks? A faulty sensor reading can be a symptom of a larger issue.

Yes, it's the ASZ engine. I haven't looked for vacuum leaks, just checked the sensor connection. Where should I look for these leaks? Are there common spots on the Alhambra that are prone to this?

Given your symptoms and the ASZ engine, a faulty manifold pressure sensor combined with a vacuum leak is probable. Getting it checked by a workshop is a sensible move.

Took the Alhambra to the shop, and you were right. It was the manifold pressure sensor. They found a big vacuum leak, as you suspected. Sensor replacement and fixing the leak cost 235€. Engine performance is back to normal. Thanks for the help!